Tank heater for respiratory mixtures used in deep diving

ABSTRACT

A tank heater for respiratory mixtures used in deep underwater diving which includes a heating coil of a plurality of counter wound wires enclosed within a sealed gas tank for heating and closely regulating the temperature of the breathing gas fed to an underwater diver. A temperature sensor is located within the tank adjacent the outlet port of the tank and is connected to appropriate electrical control circuits and a suitable power supply to control the heating coil. The tank and wires are insulated. The tank can also serve as a reserve tank of gas for the diver.

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ate ates tent 1191 [111 3,770,% Agarate 1 Nov, 6, 1973 1 TANK HEATERF9113 RESEHRATORY 3,445,677 5/1969 Leftwich 219/501 UX MIX R g USED 1BEEP [pH/ENG 3,107,669 10/1963 Gross 128/212 X 2,199,724 5/1940 Herbert.128/145 R 1 Inventor: Qhristian g e, o ex, 3,239,650 3/1966 Parks219/374 France A 7 2,515,835 7/1950 Preston 137/341 8 [73] Ass1gnee:Compagnie Francaise Des 3'344257 9/1967 Moeuer 219,3 1 x Pctroles,Paris, Compagnie FOREIGN PATENTS OR APPLICATIONS Maritime DExpertises,Marseille, 1,182,300 2 1970 Great Britain 219 375 both of France [22]Filed: Sept. 1, 1971 Primary Examiner-A. Bartis App]. No.: 176,894

[30] Foreign Application Priority Data Feb. 12, 1971 France 7104747 [52]11.8. C1 219/3741, 128/142.4, 128/212, 137/341, 219/307, 219/331,219/364, 219/381 [51] int. Cl. 11051 11/00, F24h 3 /04, A62b 7/02 [58]Field 011 Search 219/363, 359, 364, 219/366, 370-376, 379-381, 501, 306,307, 328-331; 137/341; 128/212, 142.4, 142.2, 142, 145 R [56] References(Iited UNITED STATES PATENTS 3,582,613 6/1971 Pies 219/381 2,677,7505/1954 Taylor 219/382 1,527,292 2/1925 Barlow 219/366 2,458,225 H1942Trilling et a1... 338/63 3,560,710 2/1971 Fuellemann 219/379 XAttorney-Richard C. Sughrue et a1.

[5 7] ABSTRACT A tank heater for respiratory mixtures used in deep un- 8Claims, 5 Drawing Figures United States Patent 1 Agarate Nov. 6, 1973pE/N TED afar/ m TANK HEATER FOR RESPIRATORY MIXTURES USED IN DEEPDIVING BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to a heater for use in a respiratory system forunderwater divers who are forced to operate at great depths and at lowtemperature. In particular, the present invention is directed toproviding a device to maintain the temperature of the breathing mixturethat the diver utilizes in this respiratory system, and thereby preventany caloric hemorrhage.

2. Description of the Prior Art It is known that divers working at greatdepths under low temperature and high pressure, are subject to thedangers of caloric hemorrhage due to the pressure and the cold of thebreathing mixture that they are forced to utilize in their respiratorysystem. Thus, it becomes indispensable to heat the respiratory mixturein order to assure that the divers will survive.

SUMMARY OF THE INVENTION The primary object of the present invention isto provide a respiratory mixture heating apparatus, that utilizes anair-tight tank equipped with two openings, one for the entry of thegaseous mixture and the other for its exit. The air-tight tankincorporates an electrical resistance device to heat the respiratorymixture by using either a direct or an alternating current supplydevice, in cooperation with a device for controlling the flow of currentas a function of the desired temperature. In particular, the electricalresistance utilized in the heater, is never brought to a temperaturehigher than T+ A T, where T is the desired temperature of therespiratory mixture at the entrance to the breathing ducts and A T isthe temperature rise created by the resistance heater with respect tothe temperature T, taking into account calory loss undergone by the gasat the opening of the air-tight tank with the breathing mask of thediver. The quantity of temperature represented by A T, is made as smallas possible by the choice ofa large capacity calorific resistancefilling the principal portion or capacity of the tank where the gasmixture circulates.

A principal advantage of the present invention is that it provides adevice in which none of the parts will be at a temperature that wouldcreate the risk of burning the diver, even if he, by virtue of arelatively long apnoea, causes an increase in the contact time betweenthe resistance heater and the respiratory breathing mixture.

An object of the present invention is to provide a heater device inwhich the resistance is made up of a conducting wire that is providedwith a fine insulating layer which can be folded back upon itself andwhich can be arranged inside a tank or container that is capable ofhaving a volume on the order of magnitude of the respiratory capacity ofthe diver.

By the present invention, we not only provide an extremely simple andeconomical device, but also a heating device where the temperature canbe regulated in an easy fashion, and with great precision, and whichdoes not require a large inductance coil to be introduced into thesystem with its resultant hazards to the diver.

Another object of the present invention is to provide a resistanceheater where the respiratory mixture introduced into the tank is at apressure higher than the utilization pressure employed by the diver andwhere the resistance is formed by several conducting wires with lowspecific resistance, these wires being laid out in parallel fashion.

The present invention permits the temperature regulation to be improvedby increasing the volume of gas in contact with the resistance heaterand by increasing the output of the apparatus, by increasing the contactsurface between the gas under pressure and the parallel low specificresistance conducting wires that make up the resistance heater. If thetank is a module separate from the main container of the respiratorymixture, it can also be utilized as a gas reserve which will momentarilyprovide the diver with a safety factor with which he could attempt toreach his submarine station, if for example, he is linked by a flexiblegas supply. The capacity of the tank is capable of maintaining the valueof A T very low in spite of the slight temperature drop brought about bythe pressure regulator which is necessary to supply the diver with a gasat his required pressure.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and aspects of thepresent invention will emerge more fully from the followingspecifications given here with reference to the attached drawings inwhich:

FIG. 1 is a cross-sectional view of the tank and resistance heater;

FIG. 2 is a schematic view of the electrical control circuits of thepresent invention;

FIG. 3 is a schematic view of a modification of the electrical controlcircuits of the present invention; and

FIG. 4 is a schematic view of another modification of the electricalcontrol circuits of the present invention.

FIG. 5 is a schematic drawing of a conducting wire which may be usedwith the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 discloses a tank in theform of a metallic cylinder, designed to resist both external andinternal pressure. The outside wall 24 of the tank 10, for example,resists an internal pressure of 15 bars. A clamp 25 having a bottomplate 26, is held together by bolts 27 and sealed by joints 28, to makeit possible to insure the closing and tightness of the tank. Othermethods of closing the tank can be utilized such as, a circular lid,held in place by a circular clip. Although it is possible to make thedevice of the present invention serve several divers, the preferredmanner of implementing thepresent invention is as an individualapparatus which can be easily attached to the diver by appropriatestraps. One of the advantages of using an individual device, is that thepipelines conducting the gas from the apparatus outlet to the breathingmask of the diver is thereby reduced in length and in contact with therelatively cold environmental water. This, of course, makes it possibleto lower the heat loss that would be undergone by the gas in the courseof its travel through this conduit. Various means can be utilized inattaching the apparatus of the present invention to the diver, and sinceit does not form any part of the present invention, it is not shown inthe present drawings. In addition, the

pipeline conducting the gases from the principal tank holding thebreathing mixture, with for example, a high helium content, to the inputconnection 1 shown in FIG. 1, is shown schematically. Generally thispipeline connection will utilize a non-return valve for safety featuresand to permit the tank to be utilized as a secondary reserve ofrespiratory mixture. Since the outlet pipeline is also not a relevantfeature of the present invention, it is also shown schematically asconnected to connection 2, which is located opposite connection 1.Generally, the output pipeline would lead to the pressure regulator,required to supply the diver with gas and he, in the course of aninspiration, would cause the exit of a certain variable volume of gaswhich would leave the heater apparatus. The lead wires, which connectthe resistance heater are schematically shown as connected to anelectrical supply source 3.

The electronic control circuits can be included in a printed circuitblock 4, while the assembly formed by the electric circuits can bepositioned at 5. This assmebly is advantageously cooled by the gasvolume that is entering through connection 1. The resistance heater isschematically represented by the grid shown at 6 in the drawings, simplyto make the design appear clearer. This resistance actually consists offour bundles 6A, 6B, 6C, and 6D each made up of a very long metallicwire with the low specific resistance, such as copper. In order toeliminate the thick inductance coil which would result from a simplewinding, each of the four wires illustrated as 6A, 6B, 6C and 6D isfolded back upon itself, before being inserted in bulk into the tank.Such a wire is illustrated in FIG. 5. These wires are covered with aninsulating layer 30 that can be very thin, since the temperature willgenerally never exceed a maximum temperature on the order of 40C, andsince the voltage used is relatively weak. The ends of each of' thesewires have been designated as E and F to signify that they are connectedrespectively to the terminals E and F of the supply circuit shown inFIG. 2. The wires that form the heater(6a through 6d), are connected tothese terminals, in parallel.

Referring to FIG. 2, a variable alternating voltage between 24 and 36volts is applied to the input terminal 7 and 8. A rectifier device 9 iscapable of furnishing a continuous voltage difference between the wires12 and 13 with the help of a supplemental regulation device made up ofthe resistance and the break down diode 11. A bridge circuit whichincludes the regulating potentiometers l4 and 15 in one of its branches,contains a thermistor 16, which is, as shown in FIG. 1, placed oppositethe output opening 2 of the tank. Thus, the thermistor represents thecontrol temperature adjacent the output connection 2, which leads to apipeline that connects with the divers mask. In case of any temperaturevariation, thermistor 16 will modify the conduction of transistor 17 andconsequently, that of transistor l8. Coil 19 of transformer 20 willtransmit an appropriate reaction in one direction or another to the coil21, which is connected to the terminals 22A and 22B of the currentcontroller 22. Current controller 22 is made up of a simple device,known under the name of Triac. Thus, the intensity of the currentcirculating in the wires that make up the resistance 6, is constantlycontrolled as a function of the temperature of the respiratory mixtureavailable at the output of the tank. It is clear that the temperaturecontrol device can be replaced by other equivalent devices known in theart. By

10 30, makes it possible to furnish the voltage necessary for thethermo-contact 29 in case of any cut-off of the -Triafik... .7 t .7 7

Referring to FIG. 4, the thermo-contact 29 is mounted in series with theresistance 32 to control the power transistor 33. In this modification,the power supply source is continuous. The polarity of the continuouspower supply is indicated on the schematic diagram. It should be notedthat one or more thermostatic capsules could be placed in the feedcircuit and could directly control the passage of the current into theheating element.

The bundles of wires 6a through 6d can be kept in place through meansof, for example, a perforated plate 23 made of polyvinyl chloride, orany other rigid material which may be formed integrally with asleevepositioned adjacent the interior surface of the walls 24 andoutlet end of the tank 10. Since the apparatus is generally used at agreat depth, it is designed to be thermally insulated from the ambientenvironment. For this purpose, the interior or the exterior of theapparatus is lined with the above-noted sleeve or layer of polyvinylchloride, or any other material that would serve the function ofinsulating.

By virtue of the present invention, a relatively small volume tank iscapable of heating a large volume of gas, since it provides a heatingelement with a relatively large surface. This volume'of the heatingelement constitutes an excellent means of thermal stabilization 40 whichhelps provide a regularity of operation by virtue of the very smalltemperature gradient which will be created between the heatingresistance and the respiratory gas mixture. Since the respiratory gasmixture will generally contain a high proportion of helium, this gaswill even further improve the homogenity of the temperature due to itshigh conductivity.

- s; wayarzraasrathe tank caaaw Be fliers at a pressure of 7 bars, whichwill provide, in the case of a breakdown in the main respiratory gasmixture supply, enough gas to the diver through his pressure regulatorvalve, to enable him to reach an emergency shelter. The heatingresistance wires can be copper wire with a diameter of .9mm covered witha layer of enamel with a thickness of 0.022-0.04 mm. The length 5 of thewire can be several hundred meters and can occupy a large portion of thetank capacity in which the saz i t d m u simul t n Although thepreferred embodiment has beeh de What is claimed is: 1. In a resipratorysystem for underwater divers having a breathing mixture supply and abreathing apparatus, the improvement comprising heating apparatusadapted to heat a breathing mixture as it flows from the 5 breathingmixture supply to the breathing apparatus, said heating apparatuscomprising:

a tank housing having an inlet port and an outlet port;

a porous electrical heating means in said tank housing for heating thebreathing mixture to a predetermined desired temperature, theheat-exchange surface area of said heating means being of such magnitudethat, when said heating means is maintained at a temperaturesubstantially equal to the predetermined desired temperature, abreathing mixture having an initial temperature below the desiredtemperature when introduced into said tank housing from the breathingmixture supply will have its temperature raised to be substantiallyequal to the predetermined desired temperature at said outlet port;

a source of electrical power connected to said heating means;

a sensor located within said tank housing adjacent to said outlet port,saidsensor being adapted to sense the temperature of its surroundings;and

electrical control means operatively connected to said source ofelectrical power, said sensor, and said heating means, said electricalcontrol means being adapted to be responsive to said sensor to controlthe supply of electrical power to said heating means and to maintain thetemperature of the breathing mixture at said outlet substantially equalto the predetermined desired temperature.

2. A heating apparatus as in claim 1, wherein the porous heating meansincludes at least two conducting wires electrically connected inparallel as the heater elements.

3. A heating apparatus as in claim 2, wherein each wire is folded backupon itself in said tank housing to prevent the formation of aninductance charge.

4. A heating apparatus as in claim 2, wherein each wire is insulatedwith an insulating layer of less than .1

5. A heating apparatus as in claim 1, wherein said tank housing isinsulated against heat loss to the environment and has a wall thicknesssufficient to withstand 15 bars pressure.

6. A heating apparatus as in claim 1, wherein said sensor is athermistor and said electrical control means includes a currentcontroller which is operatively connected to said thermistor.

7. A heating apparatus as in claim 1, wherein said sensor is athermo-contact and said electrical control means includes a resistor inseries with said thermocontact, a resistor in parallel with saidthermo-contact, and a current controller which is operatively connectedto said thermo-contact.

8. A heating apparatus as in claim 1, wherein said sensor is athermo-contact, said source of electrical power in DC, and saidelectrical control means includes a resistor in series with saidthermo-contact and a power transistor likewise in series with saidthermocontact.

1. In a resipratory system for underwater divers having a breathingmixture supply and a breathing apparatus, the improvement comprisingheating apparatus adapted to heat a breathing mixture as it flows fromthe breathing mixture supply to the breathing apparatus, said heatingapparatus comprising: a tank housing having an inlet port and an outletport; a porous electrical heating means in said tank housing for heatingthe breathing mixture to a predetermined desired temperature, theheat-exchange surface area of said heating means being of such magnitudethat, when said heating means is maintained at a temperaturesubstantially equal to the predetermined desired temperature, abreathing mixture having an initial temperature below the desiredtemperature when introduced into Said tank housing from the breathingmixture supply will have its temperature raised to be substantiallyequal to the predetermined desired temperature at said outlet port; asource of electrical power connected to said heating means; a sensorlocated within said tank housing adjacent to said outlet port, saidsensor being adapted to sense the temperature of its surroundings; andelectrical control means operatively connected to said source ofelectrical power, said sensor, and said heating means, said electricalcontrol means being adapted to be responsive to said sensor to controlthe supply of electrical power to said heating means and to maintain thetemperature of the breathing mixture at said outlet substantially equalto the predetermined desired temperature.
 2. A heating apparatus as inclaim 1, wherein the porous heating means includes at least twoconducting wires electrically connected in parallel as the heaterelements.
 3. A heating apparatus as in claim 2, wherein each wire isfolded back upon itself in said tank housing to prevent the formation ofan inductance charge.
 4. A heating apparatus as in claim 2, wherein eachwire is insulated with an insulating layer of less than .1 mm.
 5. Aheating apparatus as in claim 1, wherein said tank housing is insulatedagainst heat loss to the environment and has a wall thickness sufficientto withstand 15 bars pressure.
 6. A heating apparatus as in claim 1,wherein said sensor is a thermistor and said electrical control meansincludes a current controller which is operatively connected to saidthermistor.
 7. A heating apparatus as in claim 1, wherein said sensor isa thermo-contact and said electrical control means includes a resistorin series with said thermo-contact, a resistor in parallel with saidthermo-contact, and a current controller which is operatively connectedto said thermo-contact.
 8. A heating apparatus as in claim 1, whereinsaid sensor is a thermo-contact, said source of electrical power inD.C., and said electrical control means includes a resistor in serieswith said thermo-contact and a power transistor likewise in series withsaid thermo-contact.